Method for starting low-tem-perature isoolefin polymerization after solvent-cleaningthe reactor



April 21, 1953 R. F. HOWE I'AL METHQD FOR STARTING LOW-TEMPERATUREISOOLEFIN POLYMERIZATION AFTER SOLVENT-CLEANING THE REACTOR Filed Oct.1l, 1949 Patented Apr. 21, 1953 METHOD FOR STARTING LOW-TEM- PERATUREISOOLEFIN POLYMER- IZATION AFTER. ING THE REACTOR Ralph F. Howe andFrederic A. L.. Holloway, Baton. Rouge, La., assignors to Standard OilDevelopment Company, a corporation oi Dela- Ware SOLVENT-CLEAN-Application` October 11, 1949,. SerialNo.A 120,804`

` Claims. (Cl. 260,-85.3)

This invention relates to low temperature polymerization processes forolenic materials, relates particularly to continuous low temperaturepolymerization processes for the copolymerization of olens, and relates.especially .to methods, apparatus and procedures for initiating; thereaction in a. reactor newly put on stream, to. avoid the production` ofpoor polymerization initially, and produce specification grade ofpolymer from the beginning `of the operating cycle.

The basic procedure involved in this invention is well shown in U.. S.Patents No. 2,356,127 and 2,356,128', which are herewith made a part ofthis application, which` show the details of the method for thecopolyrnerization` of isobutylene with a multolefin such as butadiene orisoprene or other multiolefinl having from 4 to 14, inclusive, carbonatomsvpermolecule, the reaction being `conducted at temperatures. withinthe range between about 40 C. to about 1103i C.. this being thepreferred range, or broadly within the range between about.` -161 C. andu`164 C., the polymerization reaction being catalyzed by thev applica.-tion to the cold olefinic material of a dissolved or liquidFriedel-Crafts active metal halide catalyst.

These copolymers, particularly the copolymer of isobut-ylene withisoprene, have proven commercially satisfactory for the manufacture ofautomobile inner tubes, and several commercial plants have been builtutilizing groups of continuous reactors which are approximately 5 ft. ininternal diameter by 27 it. high, holding about 14,000 `pounds ofpolymerizate mixture. These reactors are jacketed with a liquid ethyleneas a refrigerant, producing a temperature the material within thereactor which varies between -S'FJ C., and -100 C1, depending upon theoondition of the reactor. These reactors are assembled in groups, eachreactor having a "flash tank partly filled with warm water, into which aslurry of solid polymerin diluent and unpolymerized reactants isdelivered from the reactor to flash oif the volatiles and produce awater slurry of the solid polymer; from which the solid polymer iseasilyV removed for drying and further processing. Each reactor isequipped with a powerful circulating stirrer and each group is equippedwith compressors and coolers for producing liquid ethylene, and with aseries of `fractionating towers, dryers and the like, for recovery ofthe flashed oit volatiles for recycling. Each reactor, likewise, isprovided with means for delivering thereto a supply of cold oleiinic.mixture and' a supply ofcold solution of a Friedel- 2` Crafts active`metalL halide catalyst; as is. well shown in application, Serial, No.5,i,=.5,0.99,y led July l5.. 1.944, by Joseph Nelson (now ,PatentNo.25,'17,8,56, issued December l1,` 1951,.

However, the reaction produces not only a'.

slurry of Solid polymer in diluent and reactants, but` it produces alsoa small amount oi polymer which, adheres very tightly to the interior ofthe reactor and to` the stirrer. As this layer Of adherent polymer(called by the operators foulingfV builds up. it interposes a thermalre.- sistanoe to the transfer of4 heat from the reactant mixture throughthe reactor walls to; the refrigerant; and on the stirrer itr changesthe contours of the stirrer in such a way as to re.- duce, markedly,the, rate of circulation. Accordingly after fromA fifteen hours or less,to fifty or `seventy-five hours or even longer of operation, the reactormust be cleaned of this; fouling layer. Thecleaning is preferablyconducted by the` use of `a solvent of some sort such as warm naphtha orwarm` isobutylene under pressure or the like.` In some instances thereactor must be cleaned by hand, but this is laborious,` time-consumingand expensive,` and therefore. highly undesirable.

In, any event, however, the cleaning of the reactor necessarily remo-vestherefrom the, `equilibriummixture from which there was being produced agood grade of polymer, necessarily interrupts the polymerizationreaction for a more. or less. `lengthy period of time.;^ and. inaddition.

necessitates a restarting of; the reactor when it.

has been cleaned.

During the operation of the reactor, an equiV 2.0% of4 solid, slurried,copolymer. and also an` amount of both isobutylenel and mul-tioleiinless;

than that normally present. in` the mixed f eed stream, and a percentageoi diluent; normally substantiallfl greater than the Apercentage presentin the feed stream. Also, it is` not possible to produceabsolutelypureisobutylene or absolutely pure isoprene, and accordingly,` theimpurities present in the feed stream buildup i-n the equilibriurnvmixture to substantially higher values. However. the analysis of thisreaction mixture is extremely diicult and it is commercially impossibleto duplicate it is a fresh` mixture.,

The polymerized .material discharged. from the nasi; tank contains amaior portion, but not all Of the impurities` from; the isobutylene and;iso! prene, ,since small portions of suoli impurities as;

`mitenevl4 and butenefz tend to `ooirlolymerae,.

which copolymerization sharply interferes with the over-all reaction.Accordingly, for equilibrium conditions, it is found necessary, in orderto produce `satisfactory polymer, to adjust the purity of the feedstream and the amount of catalyst in such a way as to limit interferenceof these impurities, maintaining the amount of impurity in theequilibrium mixture at a value sufficiently low to permit of themanufacture of satisfactory polymer.

When, however, a newly cleaned reactor is lled with the normal feed,very great difficulty is encountered in the productionr of satisfactorypolymer, and even greater diiculty is encountered in tne avoidance ofreactor runaways.

This situation occurs in part because of the fact that none of themultioleiins will copolymerize With isobutylene in the proportion inwhich they are present in the polymerizate mixture. Thus, a mixturecontaining 30% ybutadiene with 70% isobutylene produces a copolymer inwhich the amount of copolymerized butadiene is only about 3%. Withisoprene, there must be present about l1/3% of isoprene to produce acopolymer containing 21/% of copolymerized isoprene. Likewise, withdimethyl butadiene, somewhat less dioleiin copolymerizes than is presentin the orig.. inal picture. This situation is further Complicated by thefact that when the two materials copolymerize in a different ratio fromthat in which they are present, the proportion between the two changesas the polymerization continues, with the result that polymer made atthe beginning of the reaction is markedly'diierent from the polymerproduced when the reaction is just about complete, and accordingly, thepercentage yield is important as a factor in the control, both of thepolymer produced and in the control of the equilibrium mixture.

The other multioleiins such as myrcene, 2-methyl, 3-nonyl, butadiene,l-3 and the like, including all of the several series of substitutedbutadienes and the several analogous non-conjugated multiolens lie, intheir properties, between these extremes. Furthermore, completepolymerization of all of the unsaturates present in the discharge streamcannot be obtained while maintaining a satisfactory polymer quality.Accordingly, in continuous operation, the input stream of feed materialnecessarily must match the discharge stream in material content andproportion, and the discharge stream consists inpart of copolymerizedolens, in part of Iunpolymerized oleiins, in part of diluent and in partof extraneous materials. Also, the overflow into I Furthermore, it iscommercially unfeasible to effect a complete separation of isobutylenefrom butene-l and accordingly, the isobutylene streamdelivered to thereactor contains significant amounts of buetene-l. This is always lessthan 1%, and efforts are made, not always too successfully, to keep itbelow two-tenths of 1%. Also,rbutene-1 is a strong catalyst poison,markedly influencing the course of the reaction and markedly reducingthe molecular weight of the polymer produced; yet the butene-l is onlyslightly, if at all, copolymerized. Accordingly, the reactor contentswill of necessity build up a relatively high ratio of butene-l `toisobutylene, which must be allowed for in the reaction.

The relationship between the liquid contents of the reactor and thenormal reactor feed is approximately as shown in the following Table I:

It has been suggested that the amount of un-v saturated materials couldbe reduced in the startup mixture. This, however, is unsatisfactorybecause no proportions can be found which will match the polymerproduced at the beginning to the steady state polymer, because of theabsence of equilibrium amounts of butene-l, and the absence ofequilibrium amounts of multiolen.

According to the present invention, it is now found that if the reactoris filled from a feed stream made up of the normal diluent, in part ofisobutylene of the normal purity, with a part of the necessaryisobutylene obtained from re;

cycle material containing a higher proportion of impurities such asbutene-l and butene-2, in part with additional fresh isoprene of normalpurity and in part from recycle isoprene in about normal feed streamamount, rather than the equilibrium percentage, with a slightlyincreased amount of butene-l, a mixture is obtained which, while noteven approximately near to the equilibrium mixture, yet is so balancedin its components as to produce polymer of specification grade from theinitial production of polymer on to the end of the run. As so prepared,the starting mixture contains a small excess of diluent over the normalequilibrium mixture, about the normal to a slightly larger proportion ofisoprene and a slightly increased amount of butene-l, although thebutene-l is preferably less than 1%.

The normal catalyst is used and when the reactor is cooled, filled tooverflowing and the catalyst stream started, a period occurs duringwhich the initial stages of copolymerization occur without any tendencytowards reactor runaways, which are almost unavoidable when a reactor islled with the normal feed stock, and in addition, the first polymerproduced has the normal molecular Weight, and no abnormally highmolecular weight polymer is produced, as is unavoidable when the reactoris filled with the normal feed stream. The unexpected and rathersurprising fact thus appears that the presence of a slightly increasedamount of butene-l and a small amount of excess diluent appear tocompensate for the absence of all of the components of the equilibriumcomposition of the reaction mixture.

The supply of modified mixture from recycle material, normal fresh feedand excess isoprene .Wholly to normal feed stock. By this procedurenodefectiveapolymerjsfproduced and` a `minimum of danger of vreactorrunaways occurs, and a polymer having a molecular weight .of about60,000 and lan iodine number (bythe Wijs method) `of approximately 2.2orfany other combination `of desired :molecular Weight `and iodinenumber `is obtained `from .the beginning .of the reactor operation.

(It is :observed .that .polymerization does lnot begin .with the first`drop of 'catalyst solution, but sufficient catalyst must be added 'to`bring the concentration abovea .threshold minimum. The reason for thisnot fully known, but it may be that certain impurities in the mixturewhich combine `with the catalyst -mnst be `satised, `and it appears that:there must `be `.more than fsome `minimum concentration of catalyst toinitiate the polymerization reaction. However, these vrequirements `varyfrom minute to minute and it 4has `not ibeen found possible -ltodetermine how much catalyst solution is `required to provide a`sufliciently high concentration to start the reaction. Accordingly, theonly possible procedure is to deliver the normal catalyst stream, andwait until the reaction begins. However, with very pure reactants and arelatively small amount of diluent, the threshold value may be reachedand passed with a substantial excess before the reaction starts,whereupon there is enough catalyst in the mixture to polymerize thewhole olefinic content, which occurs within a very small fraction of asecond as a reactor runaway, resulting in the liberation of heat at amuch faster rate than it can be removed to and by the cooling jacket,and in consequence, a very dense slurry is produced at a temperaturemuch higher than normal, sometimes above the boiling point -or thediluent, and in consequence, `the polymer `is of such low grade as to beunusable. Also,such a runaway definitely Aterminates a run, and thereactor must be cleared of the defective polymer, `and the run startedover again.)

Thus the invention permits of the starting up of the low temperaturecontinuous 'polymerization reactor with a fresh `filling of reactants,free Vfrom solid polymer slurry, `without reactor runaways and withoutthe production of abnormal polymer, by a procedure of a simple butunexpected adjustment of reactor feed and reactor filling, the supply ofreactan'tsbeing shifted to the normal reactor feed when polymerizationstarts, or relatively soon thereafter.

Thus the procedure of the present invention starts a continuouscopolymerization reaction in a clean reactor by a simple adjustment ofreaction mixture and impurities, whereby reactor runaways and theproduction of defective polymer are avoided. Other objects and detailsof the invention will be apparent from the following description whenread in connection with the accompanying drawing; wherein The singlefigure is a flow diagram of the process according to the presentinvention.

:Referring to the single gure, there are proeach discharging 6 streamfand in :normal .equilibrium acondition, delivering `to .the Water in`the ashltank .3 'normal lstreams of ,slurries of solidpolymer indiluent with small percentages of unreacted oleflns The diluent andunreacted olensare volatilized, the slurry is :converted .to a slurry ofsolid ipolymer in Water which is drained ifrom thebottom of the vtankand conveyed :to lters, driers, and thezlike, for sheeting out,packaging andshipping. The `flash gas from the .flash tank 3 conveyed:to the purifying system, Where :it 4is rst compressed in a compressor4, then dried in a dried', then passed through a iirstfractionatingtower 6, from which an overheadstreamiof diluent isremoved. The Vbottoms from tower 6 pass to tower 7 `from `which anoverhead stream containing any remaining diluent and the `desired amountof recycle isobutylene'may =be removed. The bottoms from `the tower 1`are withdrawn as La purge stream to .reduce the amount `of butene-'lpresent in the `circulating system as `well =as to remove unreactedmultiolen and any undesirable heavier materials. The bottoms arepreferably delivered to a debutanizer andsent through the normalisobutylene separating system. The overhead from tower 1 is condensedand delivered to a storage drum 8.

l For those reactors which are operating normally and contain anequilibrium mixture, a portion of recycle material `from fractionatingtower 1, `comprising diluent and recycle isobutylene from the drum 8 isconveyed to a drum 9 and is there mixed'with a supply of freshisobutylene from the isobutylene puriiiers, and

with an appropriate amount of fresh isoprene and delivered under valvecontrol through a cooler (not shown) to the normally operating reactors.

Simultaneously, a solution of catalyst is prepared, preferably aluminumchloride in solution in methyl chloride (although any Friedel- Craftsactive metal halide substance in solution in any low freezingnon-complex forming solvent may be used).

(For the Friedel-Crafts catalyst, any of the active metal halidesubstances shown by N. O. Calloway in his article on the Friedel-CraftsSynthesis, printed in the issue of Chemical Reviews, published from theAmerican Chemical Society at Baltimore in 1935 in volume XVII, No. 3,the article beginning on page 327; the list being particularly 4wellshown on page 375 may be used.)

For the catalyst solvent, any low freezing noncomplex forming solventmay be used. To be low-freezing, it is merely necessary that the solventhave a freezing point below 0 C. (It is convenient, but not necessarythat the freezing point of the solvent be below the polymerizationtemperature, it being found that even though the freezing point is abovethe polymerization temperature, the catalyst solvent and the dissolvedcatalyst both dissolve in the reaction mixture before they solidify, ordissolve from the solid form.) 'Ilo be non-complex forming, it is onlynecessary that the catalyst solution show only the normal smallreduction in freezing .point and elevation in boiling pointcharacteristic of simple solutes, and that in general, the dissolvedactive metal halide can be recovered unchanged merely by evaporation ofthe solvent at approximately the normal boiling ,point of the solvent.

Whena reactor has become fouledby thezadhesion zof `a layer .of polymer`onkthe :inner surfacey the supply of feed and catalyst solution arediscontinued, the reactor emptied by any convenient method, such as thatshown in Serial No. 50,848, filed September 23, 1948, for Benoliel andFlanagan, now Patent No. 2,530,145, issued November 14, 1950, or byother methods as desired, and the interior of the reactor cleaned of theadhering polymer. When the reactor has been fully cleaned and is readyfor re-use, it is cooled to operating temperature by the delivery ofliquid refrigerant to the refrigerating jacket, and the simultaneousdelivery to the reactor of the cold special starting mixture. For thispurpose a supply of methyl chloride is taken from the storage containerIl and delivered to the feed line l2 leading to the oifstream reactor I.Simultaneously, a substantial portion to nearly all of the requiredisobutylene is taken from the storage drum 8 via a separate feed line Hlto the supply line l2. (The line I2 is preferably equipped with acooling coil surrounded by liquid refrigerant, through which thematerial passes.) Simultaneously, a. small additional amount of fresh orrecycle isoprene is delivered through a supply line I5 to the feed `linel2, and a very small amount of butene-l is delivered through a line itto the feed line l2, the butene-l being obtained from the isobutylenepurification plant, there being ample supplies available from theisobutylene purification plant. Furthermore, it is not necessary thatpure butene-l be used, merely that there be sufficient butene-l added toobtain the desired result. Under some conditions it may be desirable tosupply fresh isobutylene to the extent of part or all of the reactorcharge through lines Il and hl, replacing in part the material takenfrom storage drum 8 and at the same time to increase the amount ofbutene-l modifier added through line I6 to compensate for the higherpurity of the fresh isobutylene.

It may be noted that butane is harmless in the reaction, and thatbutene-Z is much less effective for the purpose than butene-l, andaecordingly, the presence of small quantities of butene-2 and butane maybe neglected.

The stream of modified cold feed is continued until the reactor is fulland a small stream starts to overflow. A check on the temperatureusually is desirable at this point, and if the temperature is within theappropriate range between about 90 C. and 103 C., the stream of catalystmay be started. In preparing the ycatalyst it is usually convenient totake an auxiliary stream of methyl chloride from the storage -containerH and pass it through a container having therein a substantial quantityof solid anhydrous aluminum chloride, the stream being allowed to passthrough at a leisurely rate. The result is a nearly saturated solutionof aluminum chloride in methyl chloride, which may contain from 1% toabout 31/2% 0f aluminum chloride. It is usually desirable to dilute thisrelatively concentrated stream of dissolved catalyst with enoughadditional methyl chloride from the container Il to bring theconcentration down to a value within the range between about 0.2% and1%, since higher concentrations are found to be unduly reactive, eventhough they are mixed into large quantities of the original feed.

It may be noted that when the reactor is full and the stream of catalyststarted, it may require from ten minutes to an hour to bring thecatalyst concentration up to the point where there is suficient catalystpresent to start the reaction. When the necessary amount of catalyst hasbeen added, which may be Within the range between 1 pound per thousandpounds of isobutylene, and l0 pounds per thousand pounds of isobutylene,the polymerization reaction starts.

It may be noted that with the mixtures prepared as above described, thereaction starts slowly, smoothly and easily, with no tendency of unduespeed of polymerization, which would produce a reactor runaway, and withno tendency to produce unduly high molecular weight polymer, and with notendency to produce a polymer with greater or less than the desiredamount of unsaturation as determined by the iodine number.

The above procedure has been found to be highly satisfactory andeffective in the production of the desirable polymer from the beginningto end of an operating cycle.

Alternatively, various modications may be introduced. That is, thereaction mixture may be prepared only from recycle material from storagedrum 8 without the addition of fresh isobutylene from the purificationplant. When this system is used,'a slightly somewhat greater supply offresh isoprene is required and usually a somewhat smaller amount ofbutene-l from the purification plant. As before, this procedure permitsof the adjustment of the reaction mixture to contain the desired smallexcess of butene-l and the desired excess of recycle methyl chloride.

It should be further noted that while the above procedure suggests theuse of recycle methyl chloride exclusively, this is not essential, sincefresh methyl chloride may be used interchangeably. It does not appearthat the quality of methyl chloride from the first fractionation toweris significantly different from that of fresh methyl chloride.

Also, as another alternative, the bottoms from the second fractionationtower 'I may also be used in place of the butene-l supplied from thepurification plant. This, however, is less satisfactory since the amountof butene-l and other impurities in these bottoms is not alwaysaccurately known, and much greater diniculty is encountered in making upa satisfactory start- Alternatively, also, bottoms from ing mixture. thefirst tower 6 containing isobutylene, isoprene, butene-l, and anyremaining diluent may be used directly, being strengthened somewhat withsmall quantities of additional fresh isoprene.

This procedure also is less desirable than thaty invention it is thenpossible to shift to normalreactor feed as soon as the catalyst streamisf started, or when the polymerization reaction begins, or when thereaction has reached its normal rate, as indicated by the evolution ofrefrigerant gas from the refrigerating jacket.

The preferred method, however, is to reduce the modified stream when thecatalyst stream starts, and begin the normal feed stream at about thesame time, making a gradual shift from one stream to another during thetime between the beginning of the catalyst stream and the arrival.

of normal polymerization rate. As a guide to the preparation of themodified feed stream, the

a9 -fcllowing tablekshows the .proportions of components inftheivariousparts of the system:

l10. composition `of reactants 'is maintained lsuch that the ratio ofisobutylene to butene-l is sub- Thus `the `process .of the `present.invention modifies the initial reactant ,ifeed to Aa `poly-` merization`reactor' by increasing the `amount of diluent, increasing .the amountof butene-l, decreasing theamount of Visobutylene and isoprene to.compensate `for thechange in conditions between `a `newly-cleanedreactor anda somewhat fouled reactor to prevent the Jproduction ofunsatisfactory polymer, .and `to reduce the danger ofV reactorrunaways.`

The .modiiied `feed -used for filling the reactor contains approximatelyone-fifth the normalpercentage of isobutylene, approximately twofifthsthe normal amount ,of diolen, about twice the amount of butene-l, and anincreased amount of diluent. Operating in this manner, the concentrationof olen reactants is less than onehalf the concentration of olefinicreactants in the normal reactor feed.

As can `be seen from Table II above, the modiedyfeed .as well as therecycle stream both contain substantially less isobutylene in comparisonto butene-l content than does the normal reactor liquid which has 17 .5parts of isobutylene per part of butene-l, as shown in Table II.

While there are above disclosed but a limited number of embodimentsofthe process and apparatus of the present invention, it is possible toprovide still other embodiments without departing from the inventiveconcept herein disclosed, and it is therefore desired that only suchlimitations be imposed upon the appended claims as are stated therein orrequired by the prior art.

The invention claimed is:

1. In a continuous low temperature polymerization process for thecopolymerization of isobutylene and a multiolen having from 4 to 14,inclusive, carbon atoms per molecule in the presence of a catalystsolution consisting of a Friedel-Crafts catalyst dissolved in alow-freezing, non-complex-forming solvent, the steps in combination ofsolvent-cleaning the reactor, cooling the reactor to a temperatureWithin the range between 87 C., and -103 C., simultaneously deliveringthereto a lling of reactive material containing approximately one-fththe normal percentage of isobutylene; approximately two-fifths thenormal amount of diolen; about twice the amount of butene-l, and anincreased amount of diluent, whereby the concentration of olen reactantsis less than one-half the concentration of olefin reactants in thenormal reactor feed, delivering to the iilled reactor at the desired lowtemperature a stream of liquid catalyst solution, suiiicient to initiatepolymerization, starting polymerization, continuing the catalyst streamafter start of polymerization, and gradually shifting the composition ofreactor feed to a normal value, during which shift, the

stantially less than 17.5, markedly different from the equilibrium valueof reaction `mixturein the polymerizer, relying upon themodied initialcomposition to vproduce `polymer of the same quality as is laterobtained from an `equilibrium iilling and to prevent :reactor runaways.

2. VIn `a `continuous low temperature poly-` merization process `)forthe .copolymerization Aef isobutylene and fisoprene :Lin the presence:cica catalyst Asolution .consisting of 'aluminum chloride insolution'infa low-freezing, non-complexforming solvent, :the `steps incombination :of solvent-.cleaning the reactor, `cooling the reactor to atemperature vwithin the range between -87 C., and 103 C., simultaneouslydelivering thereto `a `filling .of reactive .material containingapproximately ione-nith the normal percentage of isobutylene;.approximately twoiiiths the normal amount of dioleiin; about twice theamount of butene-l, and an A.increased amount of `diluent, whereby .theconcentration of olefin reactants is less than one-half theconcentration of olefin reactants in the normal reactor feed, deliveringto the lled reactor at the desired low temperature a stream of liquidcatalyst solution, suilicient to initiate polymerization, startingpolymerization, continuing the catalyst stream after start ofpolymerization, and gradually shifting the composition of reactor feedto a normal value, markedly different from the equilibrium value ofreaction mixture in the polymerizer, relying upon the modified initialcomposition to produce polymer of the same quality as is later obtainedfrom an equilibrium filling and to prevent reactor runaways.

3. In a continuous low temperature polymerization process for thecopolymerization of isobutylene and isoprene in the presence of acatalyst solution consisting of aluminum chloride in solution in alow-freezing, non-complexforming solvent, the steps in combination ofsolvent-cleaning the reactor, cooling the reactor to a temperaturewithin the range between 87 C., and 103 C., simultaneously deliveringthereto a lling of reactive material containing approximately one-fifththe normal percentage of isobutylene; approximately two-fths the normalamount of diolen; about twice the amount of butene-l, and an increasedamount of methyl chloride, whereby the concentration of olen reactantsis less than one-half the concentration of oleiin reactants in thenormal reactor feed, delivering to the lled reactor at the desired lowtemperature a stream of liquid catalyst solution, sufricient to initiatepolymerization, starting polymerization, continuing the catalyst streamafter start of polymerization, and gradually' shifting the compositionof reactor feed to a normal value, markedly different from theequilibrium value of reaction mixture in the polymerizer, relying uponthe modified initial composition to produce polymer of the same qualityas is later obtained from an equilibrium lling and to prevent reactorrunaways.

4. In a continuous low temperature polymerization process for thecopolymerization of isobutylene and butadiene in the presence of acatalyst solution consisting of aluminum chloride in solution in alow-freezing, non-complexforming solvent, the steps in combination ofsolvent-cleaning the reactor, cooling the reactor to a temperatureWithin the range between 87 C., and 103 C., simultaneously deliveringthereto a filling of reactive material containing approximately one-fththe normal percentage of isobutylene; approximately two-iifths thenormal amount of diolen; about twice the amount of butene-l, and anincreased amount of methyl chloride, whereby the concentration of olenreactants is less than one-half the concentration of oleiin reactants inthe normal reactor feed, delivering to the filled reactor at the desiredlow temperature a stream of liquid catalyst solution, suflicient toinitiate polymerization, starting polymerization, continuing thecatalyst stream after start of polymerization, and gradually shiftingthe composition of reactor feed to a normal value, markedly differentfrom the equilibrium value of reaction mixture in the polymerizer,relying upon the modified initial composition to produce polymer of thesame quality as is later obtained from an equilibrium lling and toprevent reactor runaways.

5. In a continuous low temperature polymerization process for thecopolymerization of isobutylene and dimethyl butadiene in the pres- 12ence of a catalyst solution consisting of aluminum chloride in solutionin a low-freezing, noncomplex-forming solvent, the steps in combinationof solvent-cleaning the reactor, cooling the reactor to a temperaturewithin the range between -87 C., and 103 C., simultaneously deliveringthereto a lling of reactive material containing approximately one-fththe normal percentage of isobutylene; approximately twofifths the normalamount of diolen; about twice the amount of butene-l, and an increasedamount of methyl chloride, whereby the concentration of olefin reactantsis less than onehalf the concentration of olen reactants in the normalreactor feed, delivering to the iilled reactor at the desired lowtemperature a stream of liquid catalyst solution, sufcient to initiatepolymerization, starting polymerization, continuing the catalyst streamafter start of polymerization, and gradually shifting the composition ofreactor feed to a normal value, markedly different from the equilibriumvalue of reaction mixture in the polymerizer, relying upon the modiedinitial composition to produce polymer of the same quality as is laterobtained from an equilibrium filling and to prevent reactor runaways.

RALPH F. HOWE. FREDERIC A. L. I-IOLLOWAY.

References Cited in the flle of this patent UNITED STATES PATENTS Number

1. IN A CONTINUOUS LOW TEMPERATURE POLYMERIZATION PROCESS FOR THECOPOLYMERIZATION OF ISOBUTYLENE AND A MULTIOLEFIN HAVING FROM 4 TO 14,INCLUSIVE, CARBON ATOMS PER MOLECULE IN THE PRESENCE OF A CATALYSTSOLUTION CONSISTING OF A FRIEDEL-CRAFTS CATALYST DISSOLVED IN ALOW-FREEZING, NON-COMPLEX-FORMING SOLVENT, THE STEPS IN COMBINATION OFSOLVENT-CLEANING THE REACTOR, COOLING THE REACTOR TO A TEMPERATUREWITHIN THE RANGE BETWEEN -87* C., AND -103* C., SIMULTANEOUSLYDELIVERING THERETO A FILLING OF REACTIVE MATERIAL CONTAININGAPPROXIMATELY ONE-FIFTH THE NORMAL PERCENTAGE OF ISOBUTYLENE;APPROXIMATELY TWO-FIFTHS THE NORMAL AMOUNT OF DIOLEFIN; ABOUT TWICE THEAMOUNT OF BUTENE-1, AND AN INCREASED AMOUNT OF DILUENT, WHEREBY THECONCENTRATION OF OLEFIN REACTANTS IS LESS THAN ONE-HALF THECONCENTRATION OF OLEFIN REACTANTS IN THE NORMAL RE-